Servomotor, zkráceně servo, je motor pro pohony (většinou elektrické, ale existují také hydraulická, pneumatická či dokonce parní serva), u kterých lze na rozdíl od běžného motoru nastavit přesnou polohu natočení osy. Servo motors are not so much a unique motor, as they are a system of mechanical-electrical components that work to control many kinds of motors. Stepper motors have inherent angular positioning, owing to their construction, and this is generally used in an open-loop manner without feedback. The Ragonnet power reverse mechanism was a general purpose air or steam-powered servo amplifier for linear motion patented in 1909..  The mechanical feedback has been replaced by an electric feedback with a position transducer. The control signal is the input, either analog or digital, which represents the final position command for the shaft. 5. A servo motor is a special subset of a continuous DC motor. The term “servo” simply means the motor operates in a closed loop control system that uses feedback from an encoder or resolver (typically integral to, or mounted on, the motor) to compare the motor’s actual position, velocity, or torque to the commanded value. Potentiometers are subject to drift when the temperature changes whereas encoders are more stable and accurate. Single-stage servo valves suffer from limitations in flow capability and stability due to torque motor power requirements. So what is a servo motor? Servo valves can provide precise control of position, velocity, pressure, and force with good post-movement damping characteristics. Ages: 20 years and up. A servo system primarily consists of three basic components - a controlled device, a output sensor, a feedback system. Typical servos can give a rotary (angular) or linear output. Two-stage servo valves may use flapper, jet pipe, or deflector jet valves as hydraulic amplifier first stages to position a second-stage spool valve. The simplest kind of servos use bang–bang control. The trade-off is a higher cost and complexity. The rotor rotates under the action of this magnetic field, and the motor’s own encoder feedback signal to the driver. Servo and receiver connections Servo control is achieved by sending a servo a PWM (pulse-width modulation) signal, a series of repeating pulses of variable width where either the width of the pulse (most common modern hobby servos) or the duty cycle of a pulse train (less common today) determines the position to be achieved by the servo. Some airliners that use these systems are the Airbus A320, A330, A340, A350, A380, Boeing 787, and Embraer E-Jet E2 family. Servo valves are often used in a feedback control where the position or force on a hydraulic cylinder is measured, and fed back into a controller that varies the signal sent to the servo valve.  On displacement-controlled applications, it usually includes a built-in encoder or other position feedback mechanism to ensure the output is achieving the desired effect.. Most commonly, two-stage servo valves use position feedback; which may further be classified by direct feedback, force feedback, or spring centering. Introduction It is tiny and lightweight with high output power. Unlike large industrial motors, a servo motor is not used for continuous energy conversion. Un servomotor de modelisme (conegut generalment com a servo o servo de modelisme) és un dispositiu actuador que té la capacitat de situar-se en qualsevol posició dins del seu rang d'operació, i de mantenir-se estable en aquesta posició. Figure 1 shows a typical PWM signal. The driver controls U/V/W three-phase electricity to form an electromagnetic field. Thus this blog discusses the definition, types, mechanism, principle, working, controlling, and lastly the applications of a servo machine. A servomotor is a specific type of motor that is combined with a rotary encoder or a potentiometer to form a servomechanism.  Steam steering engines had the characteristics of a modern servomechanism: an input, an output, an error signal, and a means for amplifying the error signal used for negative feedback to drive the error towards zero. On the high end are precision industrial components that use a rotary encoder. 4.2 out of 5 stars 42. ", https://en.wikipedia.org/w/index.php?title=Servomechanism&oldid=988282712, Articles needing expert attention from September 2013, Engineering articles needing expert attention, Creative Commons Attribution-ShareAlike License. Most hydraulic control valves are binary, they are either on or off. 4.6 out of 5 stars 179. RC servo motor is the most common … Electrical servomechanisms require a power amplifier. Modern servomechanisms use solid state power amplifiers, usually built from MOSFET or thyristor devices. A servo motor is controlled by a servo amplifier, possibly with a shaft controller. With the advantages of torque control, many applications that require precise force control for pressing, pulling and twisting motions can be accomplished. Servomotors are used for both high-end and low-end applications. Servo Motor Working Principle Before understanding the working principle of servo motor we should understand first the basics of a servomechanism. In control engineering a servomechanism, sometimes shortened to servo, is an automatic device that uses error-sensing negative feedback to correct the action of a mechanism. They operate on the principle of negative feedback, where the control input is compared to the actual position of the mechanical system as measured by some type of transducer at the output. One such example is Honeywell's servo valve which is part of the fuel control mechanism for the CFM International CFM56 engine powering the Boeing 737NG and Airbus A320 passenger aircraft.